Add support for rmn_s_r_p pattern

I really wanted to add support for a bunch more. Anything of the form S_R_P_A can be sanely written as A_S_R_P, such as "1st September 2 years ago"/"2 years ago 1st September". Enumerating all those seems a bit nuts though. Any ideas of the right approach to try and support all those patterns in a sane way?